The present invention relates to a dicing method of cutting a workpiece into the form of a lattice by using a cutting blade having an annular cutting edge.
In the production of semiconductor devices, for example, a surface of a nearly disk-like semiconductor wafer is sectioned into plural rectangular regions by cutting lines called first streets and second streets that are arranged in the form of a lattice pattern, and a predetermined circuit pattern is formed on each of these rectangular regions. The plural rectangular regions on each of which the circuit pattern has been formed are cut into individual pieces to obtain so-called semiconductor chips. The cutting of the semiconductor wafer is usually carried out by using a precision cutting apparatus called dicing apparatus. The dicing apparatus is equipped with a cutting blade 54 that is shown in FIG. 5. The cutting blade 54 comprises a base plate (hub) 541 and an annular cutting edge 542 provided on an outer peripheral portion on one side surface of the base plate 541. The cutting blade 54 that is generally called hub blade is mounted being sandwiched between a flange portion 572 of a fixing flange 57 and a holding flange 58 by fitting the a plate 541 to a tool-mounting portion 571 of the fixing flange 57 attached on a rotary spindle 56 and then by screwing the holding flange 58 onto an end of the fixing flange 57. The workpiece is moved correlative to each other to the cutting blade 54 mounted on the rotary spindle 56 in a direction at right angles to the rotary shaft of the cutting blade 54 to execute the cutting.
The dicing method of cutting the semiconductor wafer into the form of a lattice pattern by the cutting blade 54 will now be described with reference to FIG. 7. In FIG. 7, reference numeral 11 denotes a semiconductor wafer which is the workpiece to be treated, and on the surface thereof are formed plural first streets 11a in parallel with each other and plural second streets 11b formed in parallel with each other in a direction at right angles to the first streets 11a . 
Referring to FIG. 7(a), a semiconductor wafer 11 is so positioned that the first streets 11a are in a cut-feeding direction (that is a direction of moving a workpiece for cutting it) indicated by an arrow X and the cutting blade 54 is brought to a side edge of the semiconductor wafer 11. Here, the cutting blade 54 is set so that the side of the base plate 541 is on the side of an unworked region of the semiconductor wafer 11 which is the workpiece to be treated, i.e., that the side of the cutting edge 542 is located on the upstream side (upper side in FIG. 7) in an indexing direction indicated by an arrow Y1. Referring to FIG. 7(b), a forward cutting step is effected to cut the plural first streets la by sequentially and repetitively executing a cut-feeding for moving the semiconductor wafer 11 and the cutting blade 54 correlative to each other in a direction which is the cut-feeding direction indicated by an arrow X and an index-feeding for moving the cutting blade 54 in the indexing direction indicated by an arrow Y1 after one street is cut. After the forward cutting step has been finished, a rotational positioning step is executed to turn the semiconductor wafer 11 by 90 degrees as shown in FIG. 7(c), so that the second streets 1b are located in the cut-feeding direction indicated by an arrow X. At this moment, the cutting edge 542 of the cutting blade 54 is on the side of the unworked region of the semiconductor wafer 11 which is the workpiece, namely, the cutting edge 542 of the cutting blade 54 faces the downstream side (upper side in FIG. 7) in the indexing direction indicated by an arrow Y2. Then, referring to FIG. 7(d), the plural second streets 11b are cut by a return cutting step in which the cut-feeding for moving the semiconductor wafer 11 and the cutting blade correlative to each other in a direction which is the cut-feeding direction indicated by an arrow X and the index-feeding for moving the cutting blade 54 in the indexing direction indicated by the arrow Y2 after one street has been cut are executed sequentially and repetitively. According to the above-mentioned dicing method, a forward and return movement of the cutting blade 54 in the indexing direction (indicated by arrows Y1 and Y2) makes it possible to cut the semiconductor wafer 11 into the form of a lattice along the first streets 11a and the second streets 11b, whereby a very good productivity can be obtained.
In the above-mentioned dicing method, however, the cutting edge 542 of the cutting blade 54 undergoes great damage and becomes no longer usable before it is worn out. Therefore, the cutting blade must be frequently renewed, resulting in an increase of costs for the tools and for replacement.
The present inventors have conducted keen study in an effort to investigate the cause of damage to the cutting edge and have discovered the following fact. That is, though the semiconductor wafer is mounted on a frame via a tape, a pellet formed by the cutting in the forward cutting step may peel off the tape and fly when cutting of the wafer is performed by the cutting edge revolving at a speed as high as 20,000 to 30,000 rpm. The pellet 110 that peeled off may hit the outer peripheral edge 541a of the base plate 541 of the cutting blade 54 as shown in FIG. 6 to bite into the cutting edge 542 to damage the cutting edge 542. When the workpiece to be treated is a semiconductor wafer 11 of a disk-like shape, in particular, small and sharp triangular pellets are formed on the outer periphery by the dicing due to its disk-like shape. The sharp pellets 110 peel off easily because they are adhered at small contact areas on the tape 112, and bite into between the base plate 541 and the cutting edge 542 to damage the cutting edge 542.
Further, as a result of study by the present inventors, it was found that even when the pellets fly toward the side where the cutting edge 542 of the base plate 541 is provided and hit the cutting edge 542, the phenomenon shown in FIG. 6 does not occur since there is no base plate 541 and hence, the pellets that have flown do not bite into the cutting edge 542.
It is therefore an object of the present invention to provide a dicing method capable of preventing the cutting edge from being damaged by the flying pellets formed by the cutting.
In order to accomplish the above-mentioned object, according to the first invention, there is provided a dicing method of cutting a workpiece having plural first streets formed in parallel with each other and plural second streets formed in parallel with each other in a direction to intersect said first streets at a predetermined angle, along said first streets and said second streets by using a cutting blade having an annular cutting edge formed along the outer peripheral portion on one side surface of a base plate, wherein said dicing method comprises:
the first cutting step in which the plural first streets are cut by sequentially repeating the cut-feeding for positioning the workpiece so that the first streets are in the cut-feeding direction and for moving said workpiece and said cutting blade correlative to each other in the cut-feeding direction and the index-feeding for moving said workpiece and said cutting blade correlative to each other in an index direction at right angles to the cut-feeding direction to index the gap of said first streets;
a rotational positioning step in which after said first cutting step has been finished, said workpiece is turned by a predetermined angle to be positioned so that said second streets are in the cut-feeding direction, and said cutting blade is positioned at one side edge of said workpiece so that said base plate of said cutting blade faces the side of the unworked region of said workpiece; and
the second cutting step in which after said rotational positioning step has been finished, the plural second streets are cut by sequentially repeating the cut-feeding for moving said workpiece and said cutting blade correlative to each other in the cut-feeding direction and the index-feeding for moving said workpiece and said cutting blade correlative to each other in the index direction at right angles to the cut-feeding direction to index the gap of said second streets.
Further, in order to accomplish the above-mentioned object, according to the second invention, there is provided a dicing method of cutting a semiconductor wafer mounted on a frame via a tape and having plural first streets formed in parallel with each other and plural second streets formed in parallel with each other in a direction to intersect said first streets at a predetermined angle, along said first streets and said second streets by using a cutting blade having an annular cutting edge formed along the outer peripheral portion on one side surface of a base plate, wherein said dicing method comprises:
the first cutting step in which the plural first streets are cut by sequentially repeating the cut-feeding for positioning the semiconductor wafer so that the first streets are in the cut-feeding direction and for moving said semiconductor wafer and said cutting blade correlative to each other in the cut-feeding direction and the index-feeding for moving said semiconductor wafer and said cutting blade correlative to each other in an index direction at right angles to the cut-feeding direction to index the gap of said first streets;
the first rotational positioning step in which after said first cutting step has been finished, said semiconductor wafer is turned by a predetermined angle to be positioned so that said second streets are in the cut-feeding direction and said cutting blade is positioned at one side edge of said semiconductor wafer so that the base plate of said cutting blade faces the side of the unworked region of said semiconductor wafer;
the second cutting step in which after said first rotational positioning step has been finished, the plural second streets are cut over a half region from the one side edge toward the center of said semiconductor wafer by sequentially repeating the cut-feeding for moving said semiconductor wafer and said cutting blade relatively in the cut-feeding direction and the index-feeding for moving said semiconductor wafer and said cutting blade relatively in the index direction at right angles to the cut-feeding direction to index the gap of said second streets;
the second rotational positioning step in which after said second cutting step has been finished, said semiconductor wafer is turned by 180 degrees and said cutting blade is positioned at the other side edge of said semiconductor wafer so that the base plate side of said cutting blade faces the side of the unworked region of said semiconductor wafer; and
the third cutting step in which after said second rotational positioning step has been finished, he plural second streets are cut over the remaining half region from the other side edge toward the center of said semiconductor wafer by sequentially repeating the cut-feeding for moving said semiconductor wafer and said cutting blade relatively in the cut-feeding direction and the index-feeding for moving said semiconductor wafer and said cutting blade relatively in the index direction at right angles to the cut-feeding direction to index the gap of said second streets.